The American Society of Civil Engineers (ASCE) Structural Engineering Institute (SEI) guidance project for the performance of buildings under fire loads has been named the 2021 Council on Tall Buildings & Urban Habitat (CTBUH) Audience Award winner in Innovation for Tall Buildings, which was announced at CTBUH’s 18th annual awards program May 20, 2021. The project, titled Performance-Based Structural Fire Design: Exemplar Design of Four Regionally Diverse Buildings Using ASCE 7-16, Appendix E provides guidance on performance-based structural fire design (PBSFD) and was funded by the Charles Pankow Foundation. The project reviewed four building types in which one was a tall building.
The objective of this peer-reviewed project was to compare prescriptive and performance-based designs for each of the building types in terms of safety in fire as well as design, cost, and aesthetic implications. The PBSFD evaluated different performance objectives, as well as adjustments to passive fire protection and structural design to achieve the target performance.
The tall building design led by Thornton Tomasetti was for a “generic” Type I-A mixed-use, 50-story building, with approximately 20,000 square feet (1,858 square meters) per floor, representative of a common high-rise building design in the US. The building frame is steel at the lower 30 office floors, transferring to concrete framing at the upper residential floors, through a series of steel transfer trusses. Two important components of the building were considered for PBSFD: a typical bay of the steel frame of the lower 30 floors, and the transfer trusses. The team developed a series of design scenarios corresponding to varying performance objectives under uncontrolled fire exposure.
The study showed that a combination of modest structural modifications and adjustments to a code-standard quantity of fireproofing provides the designer with the best means to achieve performance goals for tall buildings. Importantly, PBSFD does not mean more expensive design. With modifications to the structure and fireproofing, a building might benefit both from better safety and reduced material costs. The design showed a reduction of up to 42 percent in fireproofing quantity. In addition, the reduced fireproofing can lower the labor cost and the installation time, compress the construction schedule, and even reduce the carbon footprint.
The results could drive changes in the safety design of tall buildings for fire safety. The team found identified safety vulnerabilities of beams, girders and their connections; determined how structural design, including changes to connections, in addition to passive fire protection, can improve the response in fire; and concluded that, in some conditions, passive fire protection without structural modifications could not provide adequate performance. The research further identified the potential for significant reduction of fireproofing in structures without compromising life safety, and the implications of designs of sensitive areas, such as transfer trusses, on global building response to fire.
Innovation Design Project Team Members:
Project Lead: American Society of Civil Engineers (ASCE) Structural Engineering Institute (SEI)
Building Type Teams: Simpson Gumpertz & Heger (SGH), Magnusson Klemencic Associates (MKA), Thornton Tomasetti (TT), and Walter P Moore (WPM)
Academic Advisory: State University of New York (SUNY) of Buffalo, Oregon State University, Johns Hopkins University, and University of Maryland.